in Albania links Lake Butrint with the Straits of Corfu
In physical geography
, a channel is a type of landform
consisting of the outline of a path of relatively shallow and narrow body of fluid, most commonly the confine of a river, river delta
. The word is cognate to canal
, and sometimes takes this form, e.g. the Hood Canal
Channel initiation refers to the site on a mountain slope where water begins to flow between identifiable banks.
[Bierman, R. B, David R. Montgomery (2014). Key Concepts in Geomorphology. W. H. Freeman and Company Publishers. United States.]
This site is referred to as the channel head and it marks an important boundary between hillslope processes and fluvial processes.
The channel head is the most upslope part of a channel network and is defined by flowing water between defined identifiable banks.
A channel head forms as overland flow and/or subsurface flow accumulate to a point where shear stress can overcome erosion resistance of the ground surface.
Channel heads are often associated with colluvium
s and landslides
is a primary factor in channel initiation where saturation overland flow deepens to increase shear stress and begin channel incision.
Overland flows converge in topographical depressions where channel initiation begins. Soil composition, vegetation, precipitation, and topography dictate the amount and rate of overland flow. The composition of a soil determines how quickly saturation occurs and cohesive strength retards the entrainment of material from overland flows.
Vegetation slows infiltration rates during precipitation events and plant roots anchor soil on hillslopes.
Subsurface flow destabilizes soil and resurfaces on hillslopes where channel heads are often formed. This often results in abrupt channel heads and landslides. Hollows form due to concentrated subsurface flows where concentrations of colluvium are in a constant flux.
Channel heads associated with hollows in steep terrain frequently migrate up and down hillslopes depending on sediment supply and precipitation.
Natural channels are formed by fluvial
process and are found across the Earth
. These are mostly formed by flowing water
from the hydrological cycle
, though can also be formed by other fluids such as flowing lava
can form lava channel
s. Channels also describe the deeper course through a reef
, sand bar
, or any shallow body of water. An example of a river running through a sand bar is the Columbia Bar
—the mouth of the Columbia river
A stream channel is the physical confine of a stream
) consisting of a bed
and stream bank
Stream channels exist in a variety of geometries. Stream channel development is controlled by both water
movement. There is a difference between low gradient
streams (less than a couple of percent in gradient or slightly sloped) and high gradient streams (steeply sloped). A wide variety of stream channel types
can be distinguished (e.g. braided river
s, wandering rivers, single-thread sinuous
rivers etc.). During flood
s, water flow may exceed the capacity of the channel and flood waters will spill out of the channel and across the valley
or drainage area
Examples of rivers that are trapped in their channels: Grand Canyon
and Black Canyon of the Gunnison
In a larger nautical context, as a geographical place name, the term ''channel'' is another word for strait
, which is defined as a relatively narrow body of water that connects two larger bodies of water. In this nautical
context, the terms ''strait'', ''channel'', ''sound'', and ''passage'' are synonymous and usually interchangeable. For example, in an archipelago
, the water between island
s is typically called a ''channel'' or ''passage''. The English Channel
is the strait between England and France.
The channel form is described in terms of geometry (plan, cross-sections, profile) enclosed by the materials of its bed and banks. This form is under influence of two major forces: water discharge and sediment supply. For erodible channels the mutual dependence of its parameters may be qualitatively described by Lane's Principle (also known as Lane's relationship): the product of the sediment load and bed grain size is proportional to the product of discharge and channel slope.
Wooden pilings mark the navigable channel for vessels entering Lake George
from the _in_[[Florida">St._Johns_River
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It is especially used as a [[nautical term to mean the dredged and marked lane of safe travel which a cognizant governmental entity ''guarantees'' to have a minimum depth across its specified minimum width to all [[Ship|vessels transiting a body of water (''see'' Buoy
). The term not only includes the deep-dredged ship-navigable
parts of an estuary
or river leading to port
facilities, but also to lesser channels accessing boat port-facilities
such as marina
s. When dredged channels traverse bay mud
or sandy bottoms, repeated dredging is often necessary because of the unstable subsequent movement of benthic soils.
[''History of the Waterways of the Atlantic Coast of the United States''](_blank)
, USACE, January 1983
Responsibility for monitoring navigability conditions of ''navigation channels'' to various port facilities varies, and the actual maintenance work is frequently performed by a third party. Storms, sea-states, flooding, and seasonal sedimentation adversely affect navigability
. In the U.S., navigation channels are monitored and maintained by the United States Army Corps of Engineers
(USACE), although dredging operations are often carried out by private contractors (under USACE supervision). USACE also monitors water quality and some remediation. This was first established under the Rivers and Harbors Act of 1899
and modified under acts of 1913, 1935, and 1938. For example, the USACE developed the Intracoastal Waterway
, and has the Mississippi Valley Division
responsible for the Mississippi River
from the Gulf to Cairo, Illinois
, the North Atlantic Division
for New York Harbor and Port of Boston
, and the South Pacific Division
for Port of Los Angeles
and Port of Long Beach
. Waterways policing as well as some emergency spill response falls under United States Coast Guard
jurisdiction, including inland channels serving port
s like Saint Louis
hundreds of miles from any coast. The various state or local governments maintain lesser channels, for example former Erie Canal
Extraterrestrial natural channels are found elsewhere in the Solar System
than the Earth
and the longest and widest of which are the outflow channels
and the channels of Venus
many of which are tens of kilometres wide (the network of channels flowing from Argyre Planitia
on Mars for example is 8000 km in length and the Baltis Vallis
Venus is 7000 km compared to the 6,650 km Nile, the largest active channel on Earth). The exact formation of these large ancient channels is unknown although it is theorised that those on Mars may have been formed due to catastrophic flooding and on Venus by lava flow. In planetary science
the term "rille
" is sometimes used for similar formations found on The Moon
that are of inconclusive origin. Channels have also been recently discovered on Titan
. The Saturnian moon has the only known liquid-filled channels in the Solar System other than Earth, the largest of which (Vid Flumina
) is 400 km in length. These are believed to be formed from flowing hydrocarbons in the hypothesized methanological cycle
[pg 71. Large Rivers: Geomorphology and Management. Avijit Gupta. John Wiley & Sons, 2007]
* Channel pattern
* Hydrology transport model
* Lava channel
* Ship canal
* Stream gradient
* Stream restoration
* Surge channel
Category:Bodies of water
Category:Coastal and oceanic landforms